19721961 has 30 divisors (see below), whose sum is σ = 34278090. Its totient is φ = 11267424.

The previous prime is 19721953. The next prime is 19721963. The reversal of 19721961 is 16912791.

It can be written as a sum of positive squares in only one way, i.e., 14288400 + 5433561 = 3780^2 + 2331^2 .

It is not a de Polignac number, because 19721961 - 2³ = 19721953 is a prime.

It is not an unprimeable number, because it can be changed into a prime (19721963) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 1485 + ... + 6453.

It is an arithmetic number, because the mean of its divisors is an integer number (1142603).

Almost surely, 2^19721961 is an apocalyptic number.

It is an amenable number.

19721961 is a deficient number, since it is larger than the sum of its proper divisors (14556129).

19721961 is an equidigital number, since it uses as much as digits as its factorization.

19721961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4995 (or 4979 counting only the distinct ones).

The product of its digits is 6804, while the sum is 36.

The square root of 19721961 is about 4440.9414542414. The cubic root of 19721961 is about 270.1780307337.

The spelling of 19721961 in words is "nineteen million, seven hundred twenty-one thousand, nine hundred sixty-one".